Abstract

The holotype of the brachyopoid temnospondyl Hadrokkosaurus bradyi, represented by a right lower jaw ramus, is re−ex−amined based upon new data and revision of various morphological features. Additional fragmentary jaw material re−ferred to this species is briefly described. Prominent features are a large postsymphyseal foramen that is anteriorly open,and prearticular and surangular buttresses for support of the articular. Brachyopoid characters include a long and robustpostglenoid area formed by surangular and prearticular, anterior and posterior keels on at least some marginal dentaryteeth, and subtriangular outline of the adductor fossa in dorsal view. Five features of the holotype ramus, long thought tobe at odds with its brachyopoid or temnospondyl nature, are critically re−evaluated. A phylogenetic analysis of lower jawcharacters in temnospondyls retrieves most of the clades found in more comprehensive data sets, but the statistical nodesupport is low. Brachyopoids are monophyletic, with Hadrokkosaurus emerging as their most basal taxon.

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Article

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The holotype of the brachyopoid temnospondyl Hadrokkosaurus bradyi, represented by a right lower jaw ramus, is re−ex−
amined based upon new data and revision of various morphological features. Additional fragmentary jaw material re−
ferred to this species is briefly described. Prominent features are a large postsymphyseal foramen that is anteriorly open,
and prearticular and surangular buttresses for support of the articular. Brachyopoid characters include a long and robust
postglenoid area formed by surangular and prearticular, anterior and posterior keels on at least some marginal dentary
teeth, and subtriangular outline of the adductor fossa in dorsal view. Five features of the holotype ramus, long thought to
be at odds with its brachyopoid or temnospondyl nature, are critically re−evaluated. A phylogenetic analysis of lower jaw
characters in temnospondyls retrieves most of the clades found in more comprehensive data sets, but the statistical node
support is low. Brachyopoids are monophyletic, with Hadrokkosaurus emerging as their most basal taxon.